1. Technical Field
The exemplary disclosure generally relates to a surface treatment method for metal substrate, and coated articles manufactured by the method.
2. Description of Related Art
To make a metal substrate appear to have a two color pattern, the metal substrate is usually treated by the following steps: a first color layer is deposited on the metal substrate by sputtering, and a second color layer is deposited on the first color layer by sputtering, the color of the first color layer is different from the color of the second color layer; portion of the second layer is masked by a shielding layer; the metal substrate is chemical etched by a etching liquid containing potassium permanganate and sulfuric acid, portion of the second layer not covered with the shielding layer is removed such that the first layer is partially exposed. However, when the concentration of the etching liquid is too high, the speed of reaction becomes too fast, causing the second color layer and the first color layer to be removed. When the concentration of the etching liquid is too low, etching liquid can etch neither the second color layer nor the first color layer. It is difficult to make the metal substrate show a two color pattern above mentioned conditions. Furthermore, even if the concentration of etching liquid is adjusted to an appropriate value, the first color layer is prone to corrosion by residual etching liquid, which will decrease the precision of the pattern.
Therefore, there is room for improvement within the art.